In the case of the machine-based cleaning, disinfection, and drying of endoscopes, one has to ensure that the very narrow endoscope channels have also been cleaned completely, and that they are not blocked wholly or partially by foreign particles that adhere to the wall of the channel.
DE 44 34 114 A1 describes a process and a device for measuring the flow resistance of a catheter in an implanted infusion system for drugs. In order to measure the patency, i.e., unobstructed flow, of the channel of the catheter, it is flushed with a predetermined volume of liquid at a predetermined pressure, whereby the period of time required for pumping this volume through the channel is measured. This predetermined volume is generated by a syringe that is capable of being hooked up to the channel of the catheter, whereby the piston of the syringe produces pressure via a spring.
EP 0 711 529 A1 describes a process and a device for checking the patency of endoscope channels. The endoscope channels are all capable of being hooked up to a common liquid container via controllable valves, whereby liquid from this container is led under pressure through the channels. The volume of liquid which flows through one or more channels per unit time is measured by means of one or more flow checking devices and compared to previous values, as a result of which it can be established whether a channel or a group of channels are patent.
It is known from DE 44 23 730 C2 that use can be made of an insertion element with controllable seals for cleaning endoscopes that have at least two channels, whereby these seals are controlled in such a way that the cleaning liquid flows through the individual channels individually. As a result of this, one ensures that the cleaning liquid flow through every channel, and that the cleaning liquid cannot drain away via other open channels if one of the channels is blocked.
In order to improve the flow through endoscope channels, U.S. Pat. No. 5,551,462 proposes an apparatus for generating increased pressure that is hooked up to the individual endoscope channels and that ensures that a cleaning liquid flows through these channels at high pressure. However, problem-free checking of the complete patency of the endoscope channels is not thereby possible.
In order to check the result after cleaning endoscopes, DE 299 03 174 U1 proposes the insertion of a test object in the machine, i.e., in addition to the endoscope, and simultaneously cleaning it and then examining the test object. If it has been cleaned in a problem-free manner, then it is assumed that the endoscope has also been cleaned in a problem-free manner. However, such an indirect test does not permit reliable conclusions to be drawn in regard to problem-free cleaning and hence in regard to the patency of the endoscope channels.
In order to measure the patency of channels, it would be possible to lead a medium under pressure (liquid or gas) through the channel and to measure the quantity of the medium flowing through the channel per unit time via a flowmeter. However, this would require very accurate flowmeters for extremely small quantities, and it is therefore technically very expensive.
Another possibility for measuring flow would comprise forcing a predetermined quantity per unit time of a medium through the channel that is to be checked, and measuring the back pressure that is produced in this way. The channel is considered to be blocked in the event of exceeding a predefined pressure value. The determination of blocking can be registered in a very simple embodiment in that a pressure producing pump becomes blocked because of the back pressure, and it then consumes a distinctly higher electric current. However, this embodiment is also very expensive or inaccurate. Both of the processes that have been described additionally require the individual connection of each individual channel to a flowmeter, a pressure meter, or a pump that are usually located in the body of the cleaning machine rather than on a support that is used for loading the machine with the endoscope. This leads, as a consequence, to the feature that every endoscope has to be connected to a corresponding number of connections, which usually amounts to between five and ten nowadays, in the washing chamber in the machine.
In general, it is also pointed out that it is not only the channels of endoscopes that can be checked with the invention but also the patency of all types of channels in items of apparatus and instruments, i.e., especially in other medical instruments as well.